The present invention relates to a method of washing an article with a high efficiency by using a single kind of washing liquid.
In manufacturing and processing articles, a washing treatment is often carried out as an intermediate treatment or a post-treatment as well as a pretreatment of materials. For instance, the washing treatment is carried out in the case of removal of chips or cutting oil after cutting of the article, a pretreatment such as degreasing in plating or a post-treatment such as removal of electroplating liquid, and a pretreatment in coating. When the number of articles to be treated is increased, a continuous conveyor system is employed. In this case, the articles are sequentially brought into a tank where a washing liquid is stored, and are passed through the washing liquid. Then, the articles are taken out from the tank, and are fed into another tank. Alternately, the articles are conveyed into a tunnel where injection nozzles for spraying a washing liquid are arranged, the articles being taken out from the tunnel after being spray-cleaned.
However, in this continuous treatment system, while the washing operation is highly efficient, a large amount of washing liquid is required and this causes some economical disadvantages. For example, treatment of waste cleaning fluid to meet pollution control requirements tends to be expensive. Additionally, in the conventional conveyor system, even if the number of articles to be treated varies from time to time, the amount of the washing liquid to be used cannot be so varied.
FIG. 2 shows a flow diagram of a multi-stage article washing process in the prior art. An article 1 is conveyed from the left-hand side, and is immersed in a washing liquid in a washing tank B-1 for 1-3 min., for example. Then, the article 1 is taken out from the tank B-1, and is similarly immersed in a washing liquid in a subsequent washing tank B-2. Then, the article 1 is conveyed to a subsequent washing tank B-3. Such a multi-stage washing system usually includes about three washing tanks. Fresh washing liquid usually is supplied first to the tank B-3 of the final stage, and is sequentially fed to the tanks of the former stages by suitable means such as a communication pipe or an overflow pipe. Finally, the washing liquid used is discharged from the tank B-1 of the initial stage. Thus, the article to be washed is moved relative to the washing liquid in a counter current manner. Accordingly, although the washing effect is improved, the amount of the washing liquid cannot be decreased even when the number of articles to be washed is small, and the washing liquid discharged out of the system often is not very dirty.
In the case where parts of a device surface-treated with chemicals are to be washed by water, a large amount of washing water is used. When the waste water must then be treated by an anti-pollution process, the costs for construction and operation of such treatment equipment are significant.